First, I would just say, I am very new to all things Linux. Coming from Windows.I thought I would try Debian on my older PC.So, I downloaded Debian 9.1, and made a bootable USB with Rufus. Lots of trouble with the installation, but finally I stopped getting errors.But - it won't boot.I don't know what info might be relevant, but here does;

I'm using the graphical installer.Before, I had two partitions, the system and data.When installing Debian I used the guided partition thingy to format and make two partitions from the system one. Swap, and the rest in '/'.When I continue it complains about No EFI partition, so I create a EFI System Partition, and set the boot flag, as I read somewhere. If I ignore this, I get an fatal error about GRUB failed to install.Everything is fine, the installation goes through, but when booting it just opens the bios.I've checked the boot options and the only one enabled, is the one named 'debian', with a UEFI label over.

I read somewhere that I should disable secure boot. But I do not have an option like that.The motherboard I'm using is a Sabertooth 990FX.

If your system is on uefi mode, take a look at the wiki page.If for some reason you have problem on uefi mode and you don't have Microsoft OS on your computer, see if you can set your motherboard on bios mode.

I have looked everywhere in the bios settings. I don't have CSM, legacy, secure mode or anything like that. And I have the newest bios version.And I don't seem to find anything in the manual to help me.

It's showed on your video. The last option. But on the other hand, it doesn't look like secure boot problem but more than gpt and uefi partition problem.I'm sorry but until now, I haven't installed linux distro on uefi mobo and I haven't experience.

I guess it happens when it can't boot. I don't know. It just goes directly to the bios.I just tried Lubuntu live on USB, and it worked fine. I then tried installing it.I still have the 'debian' option in my bios boot options. And when booting from the other option it ask me to choose 'Ubuntu' or 'Advanced Ubuntu options', when choosing 'Ubuntu', it works fine.Every other disk gives me a Windows Boot Manager error, which I guess is fine since there are no OS's on those disks.